The present invention relates to new compounds containing alkoxysilane and secondary amino groups, to a process for their preparation and to the use of the new compounds as reactants for organic polyisocyanates used in the preparation of prepolymers containing alkoxysilane and urea groups.
Hydrolyzable organofunctional silanes are key components for linking conventional polymer chemistry with silicone chemistry. Compounds of technical importance for this purpose are in particular those corresponding to the general formula EQU (RO).sub.3 Si--(CH.sub.2).sub.3 --X (R=Alkyl, X=functional group).
Such compounds contain both hydrolyzable silyl groups which cross-link by a "silane polycondensation" in the presence of moisture and other functional groups, X, which enable them to be chemically linked to conventional polymer materials. (See e.g., Angew. Chem. 98 (1986) 237-253.)
Hydrolyzable functional silanes corresponding to the above formula in which the functional group X contains Zerewitinoff active H-atoms are potentially capable of modifying polyisocyanates. (See, e.g., WO 92/05212). Commercially available products suitable for this purpose contain NH.sub.2 and/or NH groups. SH groups may also be present.
Alkoxysilanes containing SH groups are described, for example, in GB-A-1,102,251; EP-A-O,018,094; DE-A-1,162,818; U.S. Pat. Nos. 3,590,065; 3,849,471; 4,082,790; 4,012,403; and 4,401,286. All alkoxysilanes containing SH groups have the unpleasant odor which is typical of mercaptans. The polymer may, therefore, have an unpleasant odor due to residues of these compounds.
Alkoxysilanes containing amino groups are described, e.g., in J. Org. Chem. 36 (1971), p. 3120; DE-A-1,152,695; DE-A-1,271,712; DE-A-2,161,716; DE-A-2,408,480; DE-A-2,521,399; DE-A-2,749,316; U.S. Pat. Nos. 2,832,754; 2,971,864; and 4,481,364. Common to all amino-functional silanes known in the art is the disadvantage of being extremely reactive with isocyanates. These alkoxysilanes can not, therefore, be reacted with polyisocyanates due to the incompatibility, inhomogeneity and extremely high viscosities of the reaction products.
.alpha.-Aminoalkyl silane derivatives which can be cross-linked by moisture may be prepared according to German Offenlegungsschriften Nos. 1,812,504 and 1,812,562. The functional silanes described there have, however, failed to achieve technical importance due to the complicated process for their synthesis.